This is a very simple serial interface for the Icom R2 utilising the MAX233 IC. The MAX233 is a simple TTL/CMOS to RS232 level converter in a DIP package. Pin numbers in brackets are for 25 pin RS232.

Note: Ari Xirocostas found that this circuit didn’t work at all for him but he sent me a modified version which did. Ari’s version has a modified power supply to the MAX233 IC, another option would be to do away with the connection to pin 14 and instead connect an external PSU to pin 7 to provide the +5V for the IC. This may well be a better option as some serial ports may not be able to reliably power this circuit.

Icom OPC-478 Serial Cable Schematic

This schematic is for the original Icom OPC-478 cable, for use with the ICOM R2, R3 and the R-10.